Refrigeration



Jan. 4, 1944.

' P. P. ANDERSON, JR

REFRIGERATION Filed April 15, 1941 2 Sheets-Sheet 1 I-li COPPER TUBE ATTORN EY Jan. 4, 1944. ANDERSON, JR 2,338,223

REFRIGERATION Filed April 15, 1941 2 Sheets-Sheet 2 Patented Jan. 4, 1944 UNITED 1 STATES PATENT OFFICE I Philip 2. maififm. Ind. unlimito Servel, Inc., New York.

of Delaware N. Y.. a corporation Application April 15, 1941, Serial No. seam 13 Claims. (01. 62-11)) My invention relates to refrigeration, and more particularly to absorbers of absorption-type refrigeration systems.

In absorbers of the so-called film" type a film or absorption liquid is caused to form on the surfaces of piping through which a cooling medium flows. While flowing over the pipe surfaces the absorption liquid absorbs refrigerant able importance because this is one factor which determines the size of an absorber for a refrigeration system of a given capacity. In refrigeration systems of large capacity increasing the size of the absorber usually results in increasing the size of the system with which the absorber is associated, and this is objectionable because it is desirable to keep refrigeration systems as small as possible so that-they will occupy a minimum amount of space.

In refrigeration systems in which-water is employed as the cooling medium to which heat of absorption is given up in the absorber, it is desirable to employ piping formed of copper so that corrosion difficulties usually encountered in iron or steel piping are avoided. In absorbers in which piping formed of copper is employed it has been found that this metal possesses such physical properties that spreading of absorption liquid on the exterior of the piping to produce a liquid film is not promoted to the fullest extent possible. This is especially true when a water solution of whereby aliquid film will be readily produced and maintained on the exterior of the piping. More particularly, I employ copper tubing as the absorber piping and form an iron coating on the exterior surface of the tubing, so that the cooling water will contact copper and the absorption liquid will contact an iron surface. This has been found to be especially advantageous in a system in which an absorbent containing a water solution of lithium chloride is employed because of the amnity of such a solution to spread and readily form a liquid film on an iron surface.

The invention, together with the objects and advantages thereof, will be more fully understood from the following description and accompanying drawings, forming a part of this speciiication, and of which:

Fig. 1 is a view more or less diagrammatically illustrating an absorption refrigeration system embodying the invention;

Fig. 2 is an enlarged vertical sectional view,

taken on line 2-4 ofFig. 1, to illustrate the absorber more clearly;

Fig. 3 is a horizontal plan view of the absorber, with the top of the shell broken away and in section, to illustrate more clearly the manner in which absorption liquid is distributed;

Fig. 4 is an enlarged fragmentary view, taken on line 4-4 of Fig. 2, to illustrate parts of the absorber more clearly; and

Fig. 5 is an enlarged fragmentary view dia I grammatically illustrating the absorber tubing.

Referring to Fig. 1 myinvention is embodied; in a two-pressure absorption refrigeration system like that described in application Serial No.

239,762 of A. R. Thomas and P. P. Anderson, Jr.,

a lithium salt is employed as an absorbent, such as, for example, water solution of lithium chloride.

In accordance with my invention, in order to promote spreading of absorption liquid on the exterior of piping to the fullest extent possible and at the same time avoid corrosionwhen filed November 10, 1938. A system of this type operates at low pressures and includes a generator or vapor expeller l0, a condenser I I, an evaporator II, and an absorber II which are interconnected in such a manner that the pressure differential in the system is maintained by liquid columns.

The disclosure in the aforementioned Thomas and Anderson application may be considered as being incorporated in this application and, if desired, reference may be had thereto for a detailed description of the refrigeration system.

water is utilized as thecooling medium inside 7 the'piping, I employ piping having an inner sur-.,

face formed of copper and an outer surface possessing such physical properties that spreading of absorption liquid is facilitated and promoted In Fig. 1 the generator ll includes an outer shell ll within which are disposed a plurality ofvertical riser tubes ll having the lower ends thereof communicating with a space H and the upper ends thereof extending into and'above thebottom'of a vessel Il The space is within shell I! form esteem chamber about the tubes II to which steam is supplied through a conduit 20. The space l9 provides for full length heating of tubes It, a vent 2| being formed at the upper end of shell IS. A conduit 22 is connected to p the lower part of shell I5 for draining condensate from space IS.

The system operates at a partial vacuum and contains a water solution of refrigerant in ab- I sorbent liquid, suchas, for example, a water solution of about 40% lithium chloride by weight. With steam being supplied through conduit 20 to space It at atmospheric pressure, heat is applied to tubes i4 whereby water vapor is expelled from solution. The absorption liquid is raised by gas or vapor-lift action with the expelled water vaper forming a central core within an upwardly rising annulus oithe liquid. The expelled water vapor rises more rapidly than the liquid with the liquid following along the inside walls of tubes l8. The watertvapor flows upwardly through the tubes or risers it into vessel I! which serves as a vapor separatiir; Due-to baiiling in vessel It, wa-

ter vapor is separated from raised absorption so-- surface. The liquid flowing to evaporator I2 is divided in any suitablemanner for flow through the uppermost banks o1. tubes 21. The dividing of liquid may be eiiected by providing a liquid distributing trough 23 into which the liquid flows through the conduit 23. The water passes through successively lower banks of tubes through suitable end connections which are open to permit escape of vapor from the tubes, and any exis connected by a conduit 39 to vessel It, so that cess liquid is discharged from the lowermost bank of tubes 21.

The water supplied to tubes 21 evaporates therein to'produce a refrigerating or coolingeffeet with consequent absorption of heat fromthe surroundings, as from a stream of air flowin over the exterior surfaces vof the tubes 21 and fins 23. The vapor formed in tubes 23 passes out into end headers '30 which are connected at their lower ends to absorber I 4. The flash chamber 25 is provided to take care of any vapor flashing or liquid bein'i' ted to evaporator l2 through U- tube 24. -The ilashed vapor formed in the initial coolingot thefliquid flowing-from condenser ll passes-tlirouglia'conduit3i intoone of the head- '-'ers 3l"and" ihixesjwitli-vapor formed in the evaporator-12, so that disturbances in the evaporato absorber 14 fjrfrigrant "vapor is absorbed 1nd; concentrate absorption liquid which enters throug a'co fault 32, 'as will be described presentlyf The fluted absorption liquid flows through s'conamt 33; a first passage in liquid heat exchanger 34, conduit 33,vessel 38 and-con- .duit 3linto the lower space H of generator Ill.

Water vapor is expelled out of solution in generator II by heating, and the solution is raised by gas or vapor-lift action in riser tubes II, as explained above.

The absorption liquid in vessel 13 is concentrated since water-vapor has been exp lled therefrom in generator 13. This concentrated absorption liquid flows through a conduit 38, a second passage in liquid'heat exchanger 34, and conduit 32 the pressure in vessel 36 is equalizedwith the pressure in the upper part of generator [0 and condenser ll.

The heat liberated with absorption of water vapor in absorber I4 is transferred to a cooling medium, such as water, for example, which flows upward through the vertically disposed piping 40.

The cooling medium enters the lower end 01 the piping 40 through a conduit 4| and leaves the upper end of the piping 40 through a conduit 42. The conduit 42 is connected to condenser ll whereby the same cooling medium may be utilized to cool both condenser H and absorber i4, and from condenser H the cooling medium ilows through a conduit 43 to waste.

The system operates at low pressures with the generator It and condenser H operating at one pressure and the evaporator l2 and absorber i4 operating at a lower pressure, the pressure differential therebetween being maintained by liquid columns. Thus, the liquid column formed in tube 24 maintains the pressure diilerential between condenser II and evaporator l2, the liquid column in conduit 33 maintains the pressure difierential between the outlet of absorber i4 and generator i0, and the liquid column formed in conduit 32 and connected parts including conduit 38 maintains the pressure differential between the inlet of the absorber and the upper part of generator II. In operation, the liquid columns may form in conduits 33, 38, 42 and down leg of tube 24 to the levels 1:, y and z, for example. The conduits are of such size that restriction to gas flow, is effected without appreciably restricting flow of liquid.

The liquid column formed in vessel 36 and conduit 31 provides the liquid reaction head for raising liquid in riser tubes It by vapor-lift action. The vessel 33 is of suillcient volume to hold the liquid differential in the system and is of such cross-sectional area that the liquid level therein does not appreciably vary, so that a substantially banks arranged alongside of each other.

constant reaction headis provided for lifting liq- I uid in generator I.

The absorber I4 is like that described in application Serial No. 350,234 of A. R. Thomas and P. P. Anderson, Jr., filed August 3, 1940. As shown, the absorber l4 includes a cylindrical shell 44 to which is secured the lower ends of evaporator headers 30, so that vapor iormedin evaporator l2 will pass through the headers into the shell 44. Within shell 44 is the piping 43 formed to provide a plurality of vertical pipe Each pipe bank includes a plurality of substantially horizontal copper tubes 45 located one above the other and connected by bends 46. The ends '0! 1 piping 40.

The ends of the bottom, tubes 45 of eachpipe bank are connected to a manifold 50, as shown most clearly in Figs. 1 and 2. The top tubes are similarly connected at one end to another horithrough conduit .42 to condenser .l I, as explained above.

Th conduit 32 through which concentrated absorption liquid is introduced intdabsorber H terminates in a flattened or elliptical portion 52 disposed substantially at the center part of shell 44. The elliptical portion 52 is closed'at its end and to an opening in the bottom side-thereof is secured a shgrt tubular member .53 through which entering absorption liquid passes into a liquid receptacle 54'. .An annular member 55. is supported in a raised position in vessel 54 to prevent splashing of liquid entering the latter.

vThe receptacle 54. is provided with spaced transverse walls 56 to provide smaller end compartments 51 into-which liquid flows through V-shaped notches '58 in. the walls 58', as shown most clearly in Fig. 2. From the-smaller end compartments 5'! absorption liquid passes through a plurality of pipes 59 into troughs 80 which are located alongside of each other and extend prevented. In this manner drops of liquid formed at the teeth 69 fall in rapid succession onto the top surfaces of the top or highest horizontal tubes 45.

. To the bottom portions of all the horizontal tubes 45, except the tubes at the extreme bottom which are connected to manifold 50, are provided metal strips 10 which are secured to the tubes by spring clips H and provided with U- shaped loops 12. The U-shaped loops 12 form eyelets or teeth which serve as points at which drops of liquid are formed with the liquid flowin'g downwardly over the surfaces of the horizonlengthwise of the shell 44. It will be noted that i the pipes 59 lead from directly opposite end compartments 51 at each end pf vessel54,- so that absorption liquid will be supplied to the same trough 60 at regions spaced from each other. The vessel 54 is provided with a cover 65 and is supported by suitable brackets BZtothe outermost troughs 60, as shown. in Figs. 2 and 3.

The troughs 60 are 'H-shaped,. as .best shown in Fig. 2, and are supported at their .ends by tabs 63 formed at the top edges of end plates 41. The vertical pipe banks are positioned. beneath the 7 side walls 64 of the troughs to. Liquidis siphoned from the troughs. 60 onto the uppermost tubes 45 in such a manner that longitudinal. subdivision of absorption liquid is effected. -This is acconi plished by forming the outer surfaces of the .side I walls with vertical .slots 85 which 'extendfrom the top to the bottom edges of the side walls, as shown most clearly in Fig. 4.. The 'slotsj65 are in alignment with slots-.55 at the topdg'es. of the walls and slots 81 whichextend downward from tal tubes 45. The loops I2 also are as close together as possible with the spacing being such that lateral bridging of the loops with liquid is prevented. The loops 12 are preferably spaced from the top'surface portions of the tubes 45 directly beneath the loops s. vertical distance substantially the diameter of a drop of liquid.

While flowing over the outside of the horizontal tubes 45 the absorption liquid absorbs the evaporated water passing into the shell 44 from evaporator I! through the headers 30. The heat of absorption resultingfrom absorption of water vapor by the absorption solution is given up to the cooling water which flows inside the tubes 45. The diluted solution flows out from the bot tom of shell 46 into conduit 33in which the liquid stands to a height, such as :12, for example, which is dependent upon the prevailing pressure diflerential between the absorber i4 and generator ill.

In a fllm" type of absorber of the kind just 4 described it is highly important that the drops of liquid fall in rapid succession along the entire lengths of the trough side walls 64 and the hori zontal tubes .45. By insuring that liquid drops are formed at the bottom sides of the tubes, 45 a rainfall is simulated with the drops of liquid always flowing onto the top surfaces of all of the tubes including those at the bottom part oi the absorber. Any tendency for the liquid drops to run. together to produce distinct individual streams of liquid at localized areas, so that the entire peripheral surfaces of the tubes. 45. are not completely wetted. is extremely objectionable because this reduces the capacity and ability of the absorber to absorb refrigerant vapor into absorption liquid.

In order to. avoid corrosion difliculties when using water as the cooling medium, thehorizontal tubes 45 and connecting bends Mi are formed of copper. While employing tubes 45 formed of copper is a distinct advantage in that the cooling water is then contacted by a metal which is highly resistant to corrosion, it has been found that copper. possesses such physical properties ward teeth 69 formed by. notchingthe lower edges of the walls. In this manner the downwardly flowing film of liquid for'medat the. .ou'ter surfaces of the side walls 54.is-...caused .to flow toward a number of spacedv points at which drops of liquid are iormech, The teeth 68 are as close .together as possible with the spacing being such that lateral bridgingof the teeth liquid is to retain the advantage of employing coppertubing to form a passage for the cooling water and also provide a metallic surface which promotes spreading of absorption solution to maintain a satisfactory liquid film on the exterior surface of the absorber piping, the tubes 45- are formed with. an exterior iron surface. The copper tubes 45.can readily be provided with an outer layer or coating of iron by electro-plating. The

iron surface formed on the exterior of the copper ubes 45 by electro-plating is highly satisfactory, and this is especially so when using water solutions of lithium salts as an absorbent because these solutions have an aflinity for the iron, whereby spreading of such solutions is readily effected to produce and maintain liquid films over the entire exterior surfaces of the tubes. By always maintaining the entire peripheral surfaces of all the tubes in a completely wetted state, it will be apparent that the ability of the absorber to absorb refrigerant vapor is not impaired to the slightest extent, so that this factor will be extremely favorable in insuring that the absorber will be of minimum size for a refrigeration system of a given capacity.

By electro-plating an iron coating on the copper tubes 45 so that the layer of iron is integrally united with the metal forming the tube, as diagrammatically illustrated in Fig. 5, a single tube can be employed to provide inner and outer surfaces of copper and iron, respectively, whereby the fabrication of absorbers of the type described is facilitated.

It has been found that the distance between corresponding parts of adjacent loops 1! should be at least inch, so that the drip points will be located as close together as possible without lateral bridging of the space between the loops by absorption solution. With the above spacing of the drip points for aqueous solutions of lithium salts, and particularly lithium chloride solution, the drops of solution falling on to a tube having an exterior copper surface do not spread sufiiciently to merge and form a continu-: ous liquid film. However, by employing ironcoated tubes 45 of the'character described and illustrated, the absorption solution spreads sufficiently to form a continuous film, so that a desirable correlation of the spacing of the drip points and liquid film formation on the absorber tubes is effected.

While a single embodiment of the invention has been shown and described, it will be apparent that modifications and changes may be made without departing from the spirit and scope of the invention, as pointed out in the followin claims.

What is claimed is:

1. In refrigeration apparatus of the absorption type having structure for effecting gas and liquid contact including piping through which a cooking fluid is conducted, said. piping comprising substantially horizontal tubes disposed one above the other, means to supply liquid to, a region above said tubes, and means for distributing the liquid onto said tubes from said region by causing drops of liquid to fall freely by gravity from fixed points at the bottom side of each tube onto the top side of the succeeding lower tube, whereby the drops of freely falling liquid simulate a rainfall, said tubes having an inner surface of non-ferrous metal highly resistant to corrosion and an outer surface of iron to facilitate spreading of the drops of liquid falling onto the top sides of the tubes, so that the liquid will be distributed on the outer surfaces of said tubes to maintain the latter in a wetted state by films of liquid.

2. In refrigeration apparatus as set forth in claim 1 in which said tubes are formed of copper and said outer surface of iron is formed. integrally with the copper tubes.

3. In refrigeration apparatus of the absorption type having an absorber into which are.

introduced water vapor and an absorbent containing a water solution of a salt of lithium, said absorber comprising a vessel, and piping within said vessel through which a cooling fluid is conducted, said piping comprising substantially horizontal tubes disposed one above the other for effecting gas and liquid contact between said water vapor and said solution, means to supply said solution to a region above said tubes, means for distributing said solution onto said tubes from said region so that drops of liquid freely fall by gravity from fixed points at the bottom side of each tube onto the top side of the succeeding lower tube, said tubes having an inner surface containing metal highly resistant to corrosion and an outer surface containing a metal for which the solution has such an aflinity that spreading of the drops of liquid falling onto the top sides of said tubes is facilitated to maintain the latter in a wetted state by films of liquid;

4. In refrigeration apparatus of the absorption type having an absorber, connections for introducing into said absorber water vapor and an absorbent for such vapor containing a water solution of a salt of lithium, said absorber including a vessel into which said absorption solution is introduced for downward flow therein, and a conduit within said vessel upon which the downwardly flowing solution is caused to flow and through which a cooling medium is conducted, said conduit being formed of non-ferrous metal to provide an inner surface highly resistant to corrosion and an outer surface containing a ferrous metal for which said solution has such an aflinity that spreading of absorbent on the exterior of said conduit is facilitated to provide a wetted surface at which absorption of said water vapor by said solution is effected.

5. In refrigeration apparatus of the absorption-type havingstructure for effecting gas and liquid contact including piping through which a cooling fluid is conducted, said piping comprising horizontal tubes disposed one above the other, means to supply to a region above said tubes an absorbent containing a water solution of salt lithium, means for distributing the solution onto said tubes from said region by causing drops of liquid to fall freely by gravity from drip points at the bottom side of each tube onto the top side of the tube beneath it, said liquid distributing means being formed and arranged so that the drops of liquid are formed as close together as possible without lateral bridging between the drip points by the solution, said tubes being formed of one metal to provide an inner surface ,highly resistant to corrosion and an outer surface containing another metal possessing such physical properties that the drops of liquid falling on the top sides of said tubes spread sufliciently to merge and form a continuous liquid film.

6. In refrigeration apparatus of the absorption type having structure for effecting gas and liquid contact including piping through which a cooling fluid is conducted, said piping comprising "substantially horizontal tubes disposed one above the other, means to supply to a region above said tubes an absorbent containing an aqueous solution of salt of lithium, means for distributing the solution on to said tubes from said region by causing drops of liquid to fall freely by gravity from drip points at the bottom side of each tube onto the top side of thesucceeding lower tube, said liquid distributing means being so formed and arranged that the drip points are spaced approximately one-half incli apart, said tubes being formed of non-ferrous metal to provide inner surfaces highly resistant to corrosion and having outer surfaces containing iron, whereby the solution spreads sufliciently to form a continuous liquid film on said tubes. r

7. An absorption refrigeration apparatus in-' ,cluding an absorber, means for conducting into 'said absorber water vapor and an absorbent containing a water solution of a salt of lithium, said absorber comprising a vessel and piping therein through which a cooling fluid is introduced, said piping comprising substantially horizontal tubes disposed one above the other and upon the outer surfaces of which gas and liquid contact is efiected between the water vapor and the solution, means to supply the solution to a region above said tubes, means for distributing the solution ontosaid tubes' from said region so that drops of liquid freely fall by gravity from fixed points at the bottom side of each tube onto the top side of the succeeding lower tube, said tubes being formed of copper to provide inner surfaces highly resistant to corrosion, and said copper tubes having outer metallic surface formed integrally therewith and containing a. metal for which the solution has such an aflinity that spreading of the liquid falling on the top sides of said tubes is facilitated to maintain the latter in a wetted state by films of liquid.

8. An absorption refrigeration apparatus including an absorber, means for conducting into said absorber water vapor and an absorbent lution to a region above said tubes, and means for distributing the solution onto said tubes from said region so that drops of liquid freely fall by gravity from fixed points at the bottom side of each tube onto the top side of the succeeding lower tube, said tubes being formed of copper and having outer surfaces containing iron formed thereon by electro-plating, said copper'tubes providing inner surfaces highly resistant to corrosion and the solution having such an affinity for the outer electro-plated surfaces of iron that spreading of the drops of liquid falling on the top sides of said tubes is facilitated to maintain the latter in a wetted state by films of liquid.

9. Refrigeration apparatus having a wall through which heat transfer takes place between 9, film of liquid on one surface of the wall and a fluid contacting the other side of the wall, said wall being made of copper and having a coating of iron on said surface to facilitate formation of said film.

10. Refrigeration apparatus having a wall portion formed by a tube throughe which heat is transferred from a film of liquid onthe outside of said tube to a cooling medium flowing through said tube, said tube comprising a copper pipe having an exterior coating of iron to facilitate formation of said film. Y

11. Refrigeration apparatus, having a wall through which heat is dissipated from a film of liquid on the surface of the wall within the apparatus to' a cooling medium contacting the other side of said wall, said wall being made of copper and having a coating of iron formed by electrodeposition on said surface to facilitate formation and maintenance of said film.

12.. Absorption type refrigeration apparatus having an absorber wall through which heat is transferred from a film of absorption liquid on one surface of the wall to a cooling medium contacting the opposite side of the wall, said wall being made of copper and having a coating of iron on said surface to facilitate formation of said fllm.

13.-Absorption type refrigeration apparatus having an absorber wall comprising a tube through which heat is transferred from a film of absorbent liquid on the exterior surface of said tube to a cooling fluid flowing in said tube, said tube comprising a copper pipe having an external coating of iron to facilitate formation of said film. PHILIP P. ANDERSON, Jn. 

